My Ph.D research involved the processing of data from the Ozone Mapping and Profiler Suite Limb Profiler – a NASA satellite instrument designed to measure stratospheric ozone. My work involved major updates to the SASKTRAN Radiative Transfer Model (which I currently maintain), and developing algorithms to process the data. The dataset that resulted from this work has been used in a variety of projects, including the WMO Scientific Asssesment of Ozone Depletion 2018.

Currently I work on a variety of projects including:

Education

Ph. D. Physics
University of Saskatchewan
2018
Thesis: Tomographic Retrievals of Ozone with the Ozone Mapping and Profiler Suite Limb Profiler

Professional Activities

Publications

  1. Runge, E., Langille, J., Zawada, D., Bourassa, A., & Degenstein, D. (2023). Stratospheric trace gas profile retrievals from balloon-borne limb imaging of mid-infrared emission spectra. Atmospheric Measurement Techniques Discussions, 2023, 1–24.
  2. Bourassa, A. E., Zawada, D. J., Rieger, L. A., Warnock, T. W., Toohey, M., & Degenstein, D. A. (2023). Tomographic Retrievals of Hunga Tonga-Hunga Ha’apai Volcanic Aerosol. Geophysical Research Letters, 50(3), e2022GL101978.
  3. Fehr, L., McLinden, C., Griffin, D., Zawada, D., Degenstein, D., & Bourassa, A. (2023). Spherical air mass factors in one and two dimensions with SASKTRAN 1.6. 0. Geoscientific Model Development Discussions, 2023, 1–29.
  4. Dubé, K., Tegtmeier, S., Bourassa, A., Zawada, D., Degenstein, D., Sheese, P. E., Walker, K. A., & Randel, W. (2023). N 2 O as a regression proxy for dynamical variability in stratospheric trace gas trends. Atmospheric Chemistry and Physics, 23(20), 13283–13300.
  5. Godin-Beekmann, S., Azouz, N., Sofieva, V., Hubert, D., Petropavlovskikh, I., Effertz, P., Ancellet, G., Degenstein, D., Zawada, D., Froidevaux, L., Frith, S., Wild, J., Davis, S., Steinbrecht, W., Leblanc, T., Querel, R., Tourpali, K., Damadeo, R., Maillard-Barras, E., … van Malderen, R. (2022). Updated trends of the stratospheric ozone vertical distribution in the 60° S–60° N latitude range based on the LOTUS regression model. Atmospheric Chemistry and Physics Discussions, 2022, 1–28. https://doi.org/10.5194/acp-2022-137
  6. Solomon, S., Dube, K., Stone, K., Yu, P., Kinnison, D., Toon, O. B., Strahan, S. E., Rosenlof, K. H., Portmann, R., Davis, S., Randel, W., Bernath, P., Boone, C., Bardeen, C. G., Bourassa, A., Zawada, D., & Degenstein, D. (2022). On the stratospheric chemistry of midlatitude wildfire smoke. Proceedings of the National Academy of Sciences, 119(10), e2117325119. https://doi.org/10.1073/pnas.2117325119
  7. Sofieva, V. F., Szelag, M., Tamminen, J., Arosio, C., Rozanov, A., Weber, M., Degenstein, D., Bourassa, A., Zawada, D., Kiefer, M., & others. (2022). Updated merged SAGE-CCI-OMPS+ dataset for evaluation of ozone trends in the stratosphere. Atmospheric Measurement Techniques Discussions, 2022, 1–27.
  8. Dubé, K., Zawada, D., Bourassa, A., Degenstein, D., Randel, W., Flittner, D., Sheese, P., & Walker, K. (2022). An improved OSIRIS NO 2 profile retrieval in the upper troposphere–lower stratosphere and intercomparison with ACE-FTS and SAGE III/ISS. Atmospheric Measurement Techniques, 15(20), 6163–6180.
  9. Bognar, K., Tegtmeier, S., Bourassa, A., Roth, C., Warnock, T., Zawada, D., & Degenstein, D. (2022). Stratospheric ozone trends for 1984–2021 in the SAGE II–OSIRIS–SAGE III/ISS composite dataset. Atmospheric Chemistry and Physics, 22(14), 9553–9569.
  10. Dubé, K., Bourassa, A., Zawada, D., Degenstein, D., Damadeo, R., Flittner, D., & Randel, W. (2021). Accounting for the photochemical variation in stratospheric \chemNO_2 in the SAGE III/ISS solar occultation retrieval. Atmospheric Measurement Techniques, 14(1), 557–566. https://doi.org/10.5194/amt-14-557-2021
  11. Zawada, D., Franssens, G., Loughman, R., Mikkonen, A., Rozanov, A., Emde, C., Bourassa, A., Dueck, S., Lindqvist, H., Ramon, D., & others. (2021). Systematic Comparison of Vectorial Spherical Radiative Transfer Models in Limb Scattering Geometry. Atmospheric Measurement Techniques Discussions, 1–32.
  12. Dubé, K., Randel, W., Bourassa, A., Zawada, D., McLinden, C., & Degenstein, D. (2020). Trends and Variability in Stratospheric NOx Derived From Merged SAGE II and OSIRIS Satellite Observations. Journal of Geophysical Research: Atmospheres, 125(7), e2019JD031798. https://doi.org/10.1029/2019JD031798
  13. Khaykin, S., Legras, B., Bucci, S., Sellitto, P., Isaksen, L., Tence, F., Bekki, S., Bourassa, A., Rieger, L., Zawada, D., & others. (2020). The 2019/20 Australian wildfires generated a persistent smoke-charged vortex rising up to 35 km altitude. Communications Earth & Environment, 1(1), 1–12.
  14. von Clarmann, T., Degenstein, D. A., Livesey, N. J., Bender, S., Braverman, A., Butz, A., Compernolle, S., Damadeo, R., Dueck, S., Eriksson, P., & others. (2020). Overview: Estimating and reporting uncertainties in remotely sensed atmospheric composition and temperature. Atmospheric Measurement Techniques, 13(8), 4393–4436.
  15. Langille, J., Bourassa, A., Pan, L. L., Letros, D., Solheim, B., Zawada, D., & Degenstein, D. (2020). Observational evidence of moistening the lowermost stratosphere via isentropic mixing across the subtropical jet. Atmospheric Chemistry and Physics, 20(9), 5477–5486.
  16. Sofieva, V. F., Szelag, M., Tamminen, J., Kyrölä, E., Degenstein, D., Roth, C., Zawada, D., Rozanov, A., Arosio, C., Burrows, J. P., & others. (2020). Measurement report: Regional trends of stratospheric ozone evaluated using the MErged GRIdded Dataset of Ozone Profiles (MEGRIDOP). Atmospheric Chemistry and Physics Discussions, 1–20.
  17. Rieger, L. A., Zawada, D. J., Bourassa, A. E., & Degenstein, D. A. (2019). A Multiwavelength Retrieval Approach for Improved OSIRIS Aerosol Extinction Retrievals. Journal of Geophysical Research: Atmospheres, 2018JD029897. https://doi.org/10.1029/2018JD029897
  18. Langille, J., Letros, D., Bourassa, A., Solheim, B., Degenstein, D., Dupont, F., Zawada, D., & Lloyd, N. D. (2019). Spatial heterodyne observations of water (SHOW) from a high-altitude airplane: characterization, performance, and first results. Atmospheric Measurement Techniques, 12(1), 431–455. https://doi.org/10.5194/amt-12-431-2019
  19. Bourassa, A. E., Rieger, L. A., Zawada, D. J., Khaykin, S., Thomason, L. W., & Degenstein, D. A. (2019). Satellite Limb Observations of Unprecedented Forest Fire Aerosol in the Stratosphere. Journal of Geophysical Research: Atmospheres.
  20. Zawada, D. J., Rieger, L. A., Bourassa, A. E., & Degenstein, D. A. (2018). Tomographic retrievals of ozone with the OMPS Limb Profiler: algorithm description and preliminary results. Atmospheric Measurement Techniques, 11(4), 2375–2393. https://doi.org/10.5194/amt-11-2375-2018
  21. Langille, J. A., Letros, D., Zawada, D., Bourassa, A., Degenstein, D., & Solheim, B. (2018). Spatial Heterodyne Observations of Water (SHOW) vapour in the upper troposphere and lower stratosphere from a high altitude aircraft: Modelling and sensitivity analysis. Journal of Quantitative Spectroscopy and Radiative Transfer, 209, 137–149. https://doi.org/10.1016/J.JQSRT.2018.01.026
  22. Bourassa, A. E., Roth, C. Z., Zawada, D. J., Rieger, L. A., McLinden, C. A., & Degenstein, D. A. (2018). Drift-corrected Odin-OSIRIS ozone product: algorithm and updated stratospheric ozone trends. Atmospheric Measurement Techniques, 11(1), 489–498. https://doi.org/10.5194/amt-11-489-2018
  23. Sofieva, V. F., Kyrola, E., Laine, M., Tamminen, J., Degenstein, D., Bourassa, A., Roth, C., Zawada, D., Weber, M., Rozanov, A., Rahpoe, N., Stiller, G., Laeng, A., von Clarmann, T., Walker, K. A., Sheese, P., Hubert, D., van Roozendael, M., Zehner, C., … Bhartia, P. K. (2017). Merged SAGE II, Ozone_cci and OMPS ozone profile dataset and evaluation of ozone trends in the stratosphere. Atmospheric Chemistry and Physics, 17(20), 12533–12552. https://doi.org/10.5194/acp-17-12533-2017
  24. Elash, B. J., Bourassa, A. E., Rieger, L. A., Dueck, S. R., Zawada, D. J., & Degenstein, D. A. (2017). The sensitivity to polarization in stratospheric aerosol retrievals from limb scattered sunlight measurements. Journal of Quantitative Spectroscopy and Radiative Transfer, 189, 75–85. https://doi.org/10.1016/j.jqsrt.2016.11.014
  25. Zawada, D. J., Bourassa, A. E., & Degenstein, D. A. (2017). Two-Dimensional Analytic Weighting Functions For Limb Scattering. Journal of Quantitative Spectroscopy and Radiative Transfer, 200, 125–136. https://doi.org/10.1016/j.jqsrt.2017.06.008
  26. Zawada, D. J., Dueck, S. R., Rieger, L. A., Bourassa, A. E., Lloyd, N. D., & Degenstein, D. A. (2015). High-resolution and Monte Carlo additions to the SASKTRAN radiative transfer model. Atmos. Meas. Tech., 8(6), 2609–2623. https://doi.org/10.5194/amt-8-2609-2015
  27. Cheviakov, A. F., & Zawada, D. (2013). Narrow-escape problem for the unit sphere: Homogenization limit, optimal arrangements of large numbers of traps, and the N conjecture. Physical Review E, 87(4), 042118. https://doi.org/10.1103/PhysRevE.87.042118